Heater for spark plugs



.Jan. 12, 1954 L. c COUGHLIN 2,665,672

' HEATER FOR SPARK PLUGS Filed April 2, 1 952 J13 lllll lflil llllll Patented Jan. 12, 1954 UNITED STATES PATENT OFFICE 8 Claims. 1

The invention relates to improvements in heaters for spark plugs for internal combustion engines, as described in the present specification and shown in the accompanying drawings that form a part of the same.

The main object of the invention is to provide simple and efiicient means for heating the fuel gases at the point of combustion so as to facilitate the starting of the engine and to prevent the accumulation of carbon on the points of the electrodes.

A further important object of the invention is to provide means for keeping the top portions of the plugs dry and thus prevent short circuiting in the electric system.

Heretofore in devices for the purpose of preheating the fuel it has been the custom to provide each plug with a heating element, coiled or otherwise, exposed within the lower end of the shell and to feed the electric current to said heating element by means of a wire, which might or might not be an integral part of the heating element, extending upwardly through the porcelain core, or insulator, or, outwardly through the side of the metal shell, for connection with the source of electric energy, such as the battery. When the wire is conducted through the insulator it is necessary to provide a hole extending vertically through the insulator or, to provide a groove in the side wall thereof, thus greatly increasing the cost of producing the plug and in any event weakening the insulator to the extent that its life is materially shortened. When the heating wire is extended outwardly through the metal shell the cost of producing the shell is greatly increased and such a shell is not adaptable to conventional insulators.

The present invention overcomes the above enumerated, and other, disadvantages inherent in spark plug heating apparatus of known types, by constructing the heating device as a unit which is readily attachable to, and detachable from, the porcelain insulator above the shell and exteriorly of the plug, the heating of the combustion chamber being accomplished through the downward transmission by the insulator of heat applied to the exterior thereof.

A further object of the invention is to so construct the heating device that it will be readily adaptable to insulators of various sizes within reasonable limits.

A still further object of the invention is to provide simple means for grounding the heating element to the shell without welding or otherwise attaching same directly to the shell.

With the above and other objects in view the invention consists in the novel features of construction, arrangements and combinations of parts set out in the present specification and more particularly pointed out in the claims for novelty following.

In describing the invention reference will be made to the accompanying drawings, in which:

Figure 1 is an exploded view of the spark plug and heating structure in perspective.

Figure 2 is a side elevation of a spark plug with my improved heating device incorporated therewith, the latter being in central vertical section.

Figure 3 is a perspective view of my heating device, broken away and partly in vertical section.

Figure 4 is a side elevation of a portion of a spark plug, showing a heating device of slightly modified form.

Like numerals of reference indicate corresponding parts in the various figures.

Referring to the drawings and particularly first to Figures 1 to 3 inclusive, in which a complete embodiment of the invention i shown, A indicates generally a spark plug of conventional design, comprising a porcelain insulator I, carrying the usual central electrode 2, and a metal shell 3 provided with the electrode 4, the latter in properly spaced relation to the electrode 2 to provide the proper spark gap.

B indicates generally the heater assembly which has for its function the delivery of heat to the insulator I at a point above the metal shell for transmission downwardly to the combustion chamber below the lower end of the said insulator.

The heater B comprises a split band, or collar, 5 of metal or other suitable material adapted to encircle the insulator i above the shell and carrying therewithin the heating element 6, the said collar having at its ends laterally extending lugs 1 adapted when the collaris in position on the insulator to extend outwardly in closely aligned relation to one another, so that when a tubular fitting 8 is tightly wedged over the two lugs they will be drawn together and thus lock the collar securely to the insulator, with the heating element 5 in close contact with the surface of the insulator.

The heating element 6 extends from one end of the collar 5 to the other end of same and has its one end 9 turned outwardly through the collar in parallel with one lug l, to which latter it is secured by welding, or otherwise, while its other end I0 is turned outwardly preferably between the ends of the collar for grounding to the metal shell of the plug.

The heating element 6 is held spaced from the collar by means of a liner l I which may be made of asbestos or other suitable heat resisting material, placed next to the collar, and a relatively thin sheet I2 of mica, or other relatively hardersurfaced material of a non-inflammable material placed between the asbestos liner and the heating element.

The function of the asbestos liner I I is to prevent the heat cfrom escaping through the collar, while the mica or other heat resisting material having a harder surface than. that pre sented by the said liner is to hold the heating wire, or other form of heating element as for instance a metal ribbon, fully exposed for good heating contact with the surface of the insulator.

The collar 5 preferably has a top marginal portion 5a of a width equal to the combined thickness of the collar, the liner Ii, the member I2 and the heating element 6 turned inwardly to provide a flange meeting the wall of the insulator to prevent upward escape of the heat.

The preferred method of grounding the heating element 8 to the shell is by the provision Olf an annular metal member, or washer, I3 which rests on the top end of the shell below the collar 5 element connected thereto. The member I3 must, of course, be insulated from the collar and one simple method for providing such insulation is by continuing the asbestos liner I-I downwardly below the lower edge of said collar and turning such downwardly projecting portion of the liner outwardly to lie between the lower end of the collar and the member I3, as is clearly shown at I4.

The member I3 is preferably of slightly domeshape in side elevation to conform to the exterior shape of the conventiona1 metal shell at its top end and, to facilitate the securing of the end it of the heatingelement to said member, and [further to permit of ready disassembly of the device, the said member is preferably cut inwardly along opposite edges to provide a narrow neck I5 around which. the said end Id of the heating element. can be curled.

The clamp fitting 8 is provided with an outwardly tapered hollow extension I46. adapted for the reception of the electric conducting cord I'I leading from the source of electrical energy, such as the battery (not shown), there being provided a clamping member I8 of outwardly reducing diameter slidable on the tapered extension I6 and having an opening through its outer end through which the cord I? is forced, sothat the bared Wire I9 projecting from said cord within the extension I6 may be moved into electrical contact with the lugs l of the collar, to one of which lugs the end 9 of the heating element 6 is in contact.

It will thus be seen that when the electric current is admitted to the wire I9 and consequently to the heating element through the medium of a suitable switch (not shown) the heating element will cause the insulator to be heated and transmit the heat downwardly to the chamber therebelow and thus vaporise the fuel'in readiness for ignition by the spark when the engine ignition is turned on.

In Figure 4 a slight modification is shown, in. which the collar 5 has a lower marginal part 26 turned inwardly to engage the periphery of and has the end ID of the said heating the insulator, and the asbestos liner II is contained between such marginal part 20 and the top marginal part or flange 5a. In this construction the collar 5 is insulated from the washer-like member I3 by means of an annular insulating member 2i inserted between the lower flange 2t and said member I3 and preferably attached to said member I3, by means of an adhesive, or by other suitable means.

The present invention provides simple and inexpensive meansfor supplying heat to the point of combustion for fuel vaporising purposes without interfering in any way with the construction of the spark plug, so that the heater can be readily used with any of the well known types of spark plugs. Furthermore, the heating unit can be quickly disengaged from the spark plug when not required, or when the plug is to be removed.

I While the heating element is shown herein as being constructed of round wire bent to provide a multiplicity of parallel turns it is of course to be understood that the transverse sectional shape or"- the element is not material and that. such element might be of the well known ribbonshape.

While I have herein shown and described a preferred arrangement and one modification thereof, it will be readily understood that. changes and modifications therein may be found desirable or essential in meeting the various exigencies of use, and I desire to be understood as reserving the right to make. any and. all such changes or modifications as maybe found desirable or essential in. so far as the. same may fall within the spirit and: scope of the invention as expressed. in the accompanying claims when broadly construed.

What I claim is:

1. In combination, a spark plug including a metal shell and an insulator mounted in said shell and projecting upwardly therefrom, a collar encircling said insulator above and insulated from said shell, said collar having laterally turned endwise extensions providing aligned lugs, clamping means embracing said lugs for securing said collar on said insulator, said collar having a heat resisting liner, a heating element carri'ed by said collar within said liner and extending lengthwise of said collar in contact with the exterior sunface of said insulator, said heating element having one end in contact with one of said lugs, the other end of said heating element being grounded to said metal shell, and a supply wire leading from a source of electric energy to said heating element.

2. In combination, a spark plug including a metal shell and an insulator mounted in said shell and projecting upwardly therefrom, a collar encircling said insulator and insulated from said shell, said collar having laterally turned endwise extensions providing aligned lugs, an annular clamp embracing said lugs for securing said collar on said insulator, a heat resisting liner on the inner surface of said collar, a heat resisting member having a relatively harder surface than said liner arranged within said liner, an annular metallic grounding member engaging said shell below said collar and insulated from said collar, a heating, element carried by said collar and extending lengthwise of saidcollar within said, heat resisting member. and in contact with the exterior surface of the insulator, said heating element being connected at one end to one of said lugs and atits other. end being grounded. to said annularv grounding member, and a contact terminal carried by said tubular clamp connected to the supply wire of an energising electric circuit for energising said heating element.

3. A spark plug heater as set out in claim 2, wherein the said collar has a marginal portion along its top edge turned inwardly at right angles for meeting engagement with the body of the insulator.

4. A spark plug heater as set out in claim 2, wherein the said heat resisting liner extends downwardly beyond the lower edge of said collar and provides the means for insulating said annular grounding member from said collar.

5. A spark plug heater as set out in claim 2, wherein said metallic grounding member is cut inwardly from opposite side edges to provide a narrow neck to which said other end of said heating element is connected.

6. A spark plug heater as set out in claim 2, wherein said grounding member has its lower face shaped to conform substantially to the part of said shell which it contacts.

7. A spark plug heater according to claim 2, wherein said collar has a lower marginal part turned inwardly at right angles for edgewise encircling engagement with said insulator and wherein said marginal part is insulated from said annular grounding member.

8. The combination with a spark plug including a metal shell and an insulator mounted within said shell and having a part extending upwardly therefrom, an annular grounding member encircling said insulator above and in engagement with said metal shell, a collar encircling 6 said insulator above and insulated from said grounding member, said collar having opposed longitudinal marginal portions turned inwardly into edgewise encircling contact with said insulator, said collar having laterally turned endwise projections between said inturned marginal portions providing aligned lugs of lesser depth than the body of said collar, a tubular contact terminal embracing said lugs and pressing same together to secure said collar to said insulator, a liner of a heat resisting material within said collar, a heat resisting member having a relatively harder surface than said liner secured over the inner face of said liner, a heating element extending lengthwise of said collar in surface engagement with said heat resisting member and in surface contact with the exterior of said insulator, said heating element having connection at one end with one of said lugs engaged by said tubular contact terminal and at its other end being connected to said grounding member, and means for conducting electric current from an energising circuit to said heating element.

LEO C. COUGHLIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,805,040 Groves May 12, 1931 2,300,294 Iavarone Oct. 27, 1942 FOREIGN PATENTS Number Country Date 645,850 Germany June 4, 1937 

